Surface cooking unit for electric ranges



March 10, 1964 c. H. YOHE 3,124,673

SURFACE COOKING UNIT FOR ELECTRIQ 'RANGES Filed D80. 21; 1961 2 Sheets-Sheet 1 INVENTOR. CHARLES H. YOHE JZW ATTORNEY March 10, 1964 c. H. YOHE 3,124,673

SURFACE COOKING UNIT FOR ELECTRIC RANGES Filed Dec; 21. 1961 2 Sheets Sheet 2 /3a.2 w): m

y /////////////A 40 34 as INVENTOR: CHARLES H. YOHE ATTORNEY United States Patent 3,124,673 SURFACE COGKING UNIT FOR ELECTRIC RANGES Charles H. Yohe, Glen Ellyn, llL, assignor to General Electric Company, a corporation of New York Filed Dec. 21, 1961, Ser. No. 161,230 3 Claims. (Cl. 219-37) This invention relates to heating units for surface cooking operations on an electric cooking range, and in particular to a mechanism for mounting the heating element thereof in a manner which permits substantially unrestrained lateral expansion and vertical movement.

For many years the surface cooking units of electric ranges have consisted of one or more resistance heating elements of the sheathed tubular type wound in the form of a flat spiral. In recent years the heating element sheath has been substantially reduced in diameter, and after coiling, has been compressed into approximately semicircular shape. In Vallorani et al., 2,662,158, granted December 8, 1953, for Heating Unit and Method of Making the Same, assigned to my present assignee, the maximum inside diameter of the sheath is of the order of .240 inch and the flat top surface of the sheath has a width of the order of .220 inch. The advantages of this small diameter and wide top are that the heating element is quite light and flexible, has relatively small mass, and therefore small heat inertia, and presents maximum heated surface in contact with the cooking vessel placed thereon. The said Vallorani et a1. patent provides for ecuring the heating unit to a supporting spider by a single spider-mounted fixture having jaw portions which are staked to the sheath at only one point along its length. As is known in the art, the staking is accomplished by causing the opposed jaws to tightly engage angular shoulders on opposite sides of the sheath. The purpose of this single point of attachment is to free the remainder of the sheath for lateral displacement as the sheath expands or contracts during heating or cooling.

It has been determined, however, that the staking operation may weaken the sheath at the points of staking with resultant possibility of fracture in subsequent use. It was further found that because the sheath becomes extremely hot during a cooking operation, the small jaws of the gripping fixture also get hot, weaken, and eventually loosen under the forces exerted by the expansion of the sheath.

The present invention provides means for rigidly securing the heating unit coils relative to a support spider, by a rigid bracket extending from the spider to securely engage the relatively cool terminal portion of the sheath. The bracket is formed with a collar through which the terminal portion extends, and this collar is secured to the terminal portion of the sheath by a hexagon crimp, that is, a crimping operation which compresses the collar and the sheath engaged thereby, into an hexagonal shape, it being understood that the semi-circular formation of the heating element does not extend to the terminal portions. This form of attachment is mechanically very secure and does not permit the sheath to rotate relative to the bracket. After the crimping operation, the circular sheath above and below the collar is slightly larger than the sheath portion engaged by the collar, and the sheath is thus securely held against vertical displacement. After the crimping operation the coil surfaces are arranged to occupy a common horizontal plane relative to the plane of the supporting spider, and the brackets are thereupon welded to an arm of the spider. By appropriate fixtures and gauging operations well known to those familiar with the art, the respective coils are accurately aligned relative to the spider; and the accuracy of placement of the brackets on the spider, coupled with the fact that the 3,124,673 Patented Mar. 10, 1964 initially tight engagement of the bracket with the sheath is not subject to stresses resulting from wide temperature variations, insures that the original alignment of the heating element will endure.

It is, therefore, a feature of the invention that the respective heating element coils are securely held at the cool terminal ends thereof. As will later appear, the coil supports are nevertheless relatively close to the actual operating surface of the heating elements coils and are of sufficient structural rigidity to insure that the brackets cannot distort under service. The coils have relatively free lateral movement and a suitable degree of vertical adjustability. This latter aspect is of importance because as a practical matter many cooking vessels have bottoms which are slightly concave or convex and the conventional rigidly secured heating elements cannot easily conform to irregular bottom surfaces of the cooking vessels. The present method of securement of the heating elements affords a freedom of lateral and vertical movement which causes the coils readily to conform to the irregularities of the bottom of the cooking vessel. This obviously im proves the heat transfer from the heating elements to the vessel. I am aware that flexibility of the coils of a heating element has been sought in the prior art. I know of no art, however, which relates the heating unit to the upporting spider so that the coils of the unit when at rest are spaced slightly above the surface of the spider and have substantially unrestrained freedom for lateral and vertical adjustment whereby under the Weight of the cooking vessel and freedom for lateral movement under expansion forces, the coils can adjust for maximum surface contact with the vessel.

It is therefore an object of the invention to provide means for securing a sheathed heating unit to a supporting spider in a manner which causes a substantially hexagonal deformation of the sheath of the heating element and its supprting bracket whereby the sheath is secured in a manner preventing longitudinal or rotative displacement relative to the securement means.

It is another object of the invention to provide a means for securely mounting a coiled heating unit relative to a supporting spider while permitting substantial freedom for lateral and vertical movement of convolutions of such heating element.

Other features and advantages of the invention will be apparent from the following detailed description read in connection with the accompanying drawings in which:

FIG. 1 is a plan view of a heating unit constructed according to the present invention, showing only fragmentary portions of the cooking range structure;

FIG. 2 is a side sectional elevation taken on lines 22 of FIG. 1;

FIGS. 3 and 4 are somewhat schematic plan and sec tional elevations respectively, showing a fixture for the attachment of mounting brackets to terminal portions of one of the elements of the heating unit. FIG. 4 is taken on lines 4-4 of FIG. 3 and the crimping tools of FIG. 3 are not present in FIG. 4; and

FIG. 5 is an enlarged sectional elevation of the heating element taken on lines 55 of FIG. 3.

Referring now to FIGS. 1 and 2, the cooking top 1 of a domestic electric range, shown in fragmentary portion, is formed with a circular opening 2 defined by the inwardly flange 3. The Well defined by the flange 3 and the vertical wall 4 accommodates an electric heating unit; specifically, the well accommodates the circular trimring 5 through the vertical wall 6 of which pass extremities of the legs 7, 8, 9 and it) of a heating unit supporting structure 11 known in the art as a spider. Although the arms 7, 8 and 10 may be of any cross sectional shape providing a smooth upper edge, at least a portion of the arm 9 should have vertical side walls to accommodate the brackets later described. It will be understood that the upper edges of all of the arms are in a common plane. As indicated in FIG. 1, the outermost extremity 9.1 of leg '9 is ofiset and there is pivotally attached thereto an upstanding element 12 of a hinge 13. The upstanding element 14 of the hinge is bifurcated to accommodate the passage of a screw 15 by means of which the spider is attached to the adjacent wall 4- of the range. It will be noted that the trim ring 5 positions the spider so that the uppermost edges of the respective arms occupy a plane above but parallel to the cooking top 1. This structure is essentially conventional. Also conventional is the reflector pan 16 removably supported by its rim on flange 3.

The actual heating unit comprises two coiled resistance heating elements, of the metallic sheath type. Coil 1'8 commences at terminal portion 20, rises to substantially the level of the top of the spider and then runs as a fiat spiral to terminate in the other terminal 21 where it drops vertically and then extends horizontally as shown in FIG. 2. The juncture between the flat coil portions and the vertical terminals is a smooth 90 curve. The ho Zontal portions of the terminals 20 and 21 preferably occupy a common plane. Coil 22 commences at terminal portion 23 which reaches to the top of the spider, then runs in a fiat spiral to terminate at the downwardly extending terminal 24. Terminals 23 and 24- have horizontally extending port-ions which occupy a common plane. In the illustrated embodiment the horizontal portions of terminals 20 and 23 are in a common vertical plane, as are the horizontal portions of terminals 21 and 24. Also, the actual electrical terminal pins 2.1.1 and 24.1 protruding from the ends of the sheath are electrically interconnected by means of the rigid link 25; the actual terminal pin 20.1 has a connection lug 26 connected thereto and the terminal pin (not shown) which protrudes from the terminal portion 23 has a connection lug 27 connected thereto. The link 25 and the lugs 26 and 27 provide for connecting the respective coils in various parallel and series relationships across a 230 volt A.C. Edison power supply to obtain various wattage outputs, as well understood in the art.

Referring now to FIG. 5, the respective heating elements include the outer metallic sheath 28 which has a relatively thin wall and is usually of a nickel-chromiumiron alloy. Also, the heating element includes the resistance conductor 30 fixed within the sheath by being imbedded in a highly compacted mass 31 of an electrically insulating and heat transmitting material such as finely divided magnesium oxide. The sheath is initially circular and the resistance conductor 30 is in the form of a circular helix; after amxing terminal pins thereto the helix is arranged within the tubular sheath, which is then in a vertical posture, and the sub-assembly filled with powdered magnesium oxide in a machine such as that disclosed in Andrews Patent No. 2,316,659, of April 13, 1943. The filled sheath which is then known in the art as a winding, is rolled to reduce the diameter of the sheath and compact the magnesium oxide. The winding is then annealed, coiled and flattened to produce the substantially semi-circular shape of FIG. 5. It will be understood that the terminal portions of the sheath are not flattened and therefore maintain a circular cross section. During the coiling and flattening operation the resulting flat upper surface of the several coils of the heating element sheath is established in a common horizontal plane, and the horizontal runs of the terminal ends of the sheath are brought into parallelism with said plane and are given the desired vertical spacing relative thereto.

In passing, it will be noted that all of the terminal pins such as typified by the terminal 24.1 in FIG. 2, and pins 20.1 and 2 1.1 in FIG. 3, extend to substantially the actual working surface of the heating element, at which point the resistance conductor 30 begins. Therefore the terminal pins and the terminal portions of the sheath do not get hot because the pins are of relatively large diameter and have substantially current carrying capacity.

Referring now to FIG. 4, the heating element 18 is in a fixture for the application of support bracket 33 to the vertical portion 2.1.2. of the sheath terminal portion 21. The bracket has a flat base 34 and an attachment wall 35 extending upwardly therefrom in a precise perpendicular relationship therewith. The bracket also has an extruded collar 36 sized to snugly accommodate the sheath portion 21.2. It will be noted that the base 34 is of relatively small area and that the passage .of the sheath through the collar is quite close to the junction of the bracket portions 34- and 35. These structural aspects provide a bracket which is very rigid and resistant to bending relative to the spider arm to which it will be attached.

This sub-assembly is then placed in a fixture such as 37 to provide for accurately gauging the position and orientation of the bracket 33. The fixture 37 may have its upper surfaces 37.1 and 37.2. grooved in conformity with the ultimate spiral shape of the heating element whereby when the element is positioned and the clamps or retainers 38.1 and 38.2 applied, the heating element will be held in its ultimate operating shape. Also, the fixture 37 has a channel 44); said channel is slotted as at 41 to snugly accommodate the passage of the vertical portion 21.2 of the sheath terminal. A gauging block 42 extends upwardly from the base of the channel 40'; the front surface of said block as viewed in FIG. 4 is precisely vertical relative to the channel base and is forward of the longitudinal center line of the spider arm 9 by one half oi" the thickness of said arm.

With the heating element firmly within the fixture 37 the bracket 33 is adjusted so that its base seats on the base of the channel 4d (the bracket base 34 reaches across the slot 41 of the channel and is therefore secure on the channel base) and the support wall 35 is pressed firmly against the surface of the gauging block 42. The jaws 44, 46, or a conventional crimping tool (not shown) are then driven against the collar 36. Each of the jaws has an operating end defining approximately one half of a hexagon, whereupon the jaws impart a hexagonal shape to the collar 3b and in lesser but nevertheless effective degree, to the sheath of the heating element within the collar. In view of the fact that the heating element sheath is circular immediately above and below the collar, and the crimping operation has distorted the collar and sheath inwardly, the resulting attachment of the bracket to the sheath locks the bracket against axial or rotatiye displacement relative to the sheath; The center of the collar is spaced from the Wall 35 by less than the diameter of the sheath. The moment arm between the collar and the wall 35 is thus substantially at a minimum, making it impossible, in a practical sense, to bend the base 34 of the bracket by effort applied to the terminal portion. The heating element may be removed (from the fixture 37 without danger of accidental displacement of the bracket 33.

It will be understood that the heating element 22 is placed in a fixture (not shown) appropriate to its own configuration so that its own mounting bracket 50 (FIG. 1) may be precisely positioned and similarly crimped to the 'vertical portion of the sheath terminal 23.

The support spider L1 is then placed in a suitable fixture (not shown) and the heating elements 18 and 22 placed thereon in their desired intertwined relationship. In this relation-ship the respective brackets 33 and 50 will be on opposite sides of the arm 9 and the bottoms of the bracket are exactly related to the bottom edge of the arm 9. As shown, the brackets are at this bottom edge, whereupon both brackets can bottom on the base wall of the fixture on which the spider is resting. Desirably, the position of the brackets on their respective terminals is such that in this relationship to the bottom edge of the spider arm the plane of the bottom edges of the heating elements is parallel to the plane defined by the top edges of the spider arms but slightly above said edge,

The upstanding walls of the bracket are then secured to the side wall surfaces of the arm 9 by conventional spot welding techniques.

It will be noted that each of the heating elements is fixed to the spider at only one of its terminal portions, whereby the coil portions of the elements which cooperatively form the supporting area for a p an or other cooking vessel (not shown) are comparatively free to expand or contract in the plane of the supporting area. This freedom of movement plus the freedom to deflect under the weight of the pan, provide a substantial measure of adaptability to irrregulanities of the bottom of the pan. If, for example, the pan has a slight convexity, the central coils of the heating elements will deflect downwardly to the extent permitted by the clearance relative to the supponting spider, whereas the outermost convolutions may engage the bottom of the vessel without deflection. Similarly, a pan having a slightly concave bottom will deflect the outer convolutions while leaving the inner ones in normal engagement with the pan bottom. The bases of the respective brackets are of relatively small area, and of sufficiently thick stock to make them inherently rigid and resistant to bending or deformation, and the close proximity to the arm of the spider affords protection against being accidentally struck during any subsequent operation associated with the manufacture of the range. The hexagonal shape of the engagement of the collars to the sheath, and the relatively cool area at which these brackets are secured to the sheath, prevent the loosening of the bracket relative to the sheath under conditions of expansion .or contraction and thus prevent any possibility of axial or rotational displacement of the heating elements relative to their supporting brackets.

While there has been described what is at present thought to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

I claim as my invention:

1. A heating unit for surface cooking operations on an electric cooking range, comprising, in combination:

at least one heating element of the sheathed resistance conductor type arranged in a flat spiral coil, the sheath of said element throughout said coil portion thereof having a flattened upper portion defining a horizontal plane to provide a platform for the support of a cooking vessel,

terminal end portions of said sheath extending vertically downwardly from said plane and being of circular cross section;

support means including structure having a plurality of radially extending arm members extending beyond the radially outermost convolution of said spiral coil and presenting coil-supporting surfaces in a horizontal plane;

and means for securing said heating element to said support means with the sheath of the spiral coil portion thereof free of said arm members to permit substantially unrestrained lateral and vertical movements of the flat spiral coil portions of said heating element, said securing means including a horizontally disposed first bracket element accommodating the passage therethrough of one of said circular terminal portions, said bracket element having a substantially hexagonal collar, wall portions of which grip said sheath to distort a portion thereof intermediate upper and lower circular portions into a polygonal shape conforming to said collar wall portions to prevent rotational or axial displacement of said sheath relative thereto,

and a vertical second bracket element fixed to a side wall of one of said bracket members to establish the first and bracket element at a fixed distance below.

the plane occupied by the flat spiral coil portion of said heating element,

said collar being spaced from said second bracket ele ment by less than the diameter of said sheath.

2. A heating unit for surface cooking operations on an electric cooking range, comprising, in combination:

a pair of heating elements of the sheathed resistance conductor type arranged in a flat spiral coil, the sheath of each of said elements throughout the spiral coil portion thereof being in a common horizontal plane to collectively provide a platform for the support of a cooking vessel,

terminal end portions of each of said sheaths extending vertically downwardly from said plane and being of circular cross section;

support means including structure having a plurality of radially extending arm members extending beyond the radially outermost limit of said platform and presenting coil-supporting surfaces in a horizontal plane,

at least one of said arm members having vertical side wall portions;

and means individual to each heating element for securing said heating elements to said support means whereby the platform defined thereby is related to theplane of said arm members to permit substantially unrestrained lateral and vertical movements of the flat coil portions of the respective heating elements relative to said arm members, each said securing means comprising only a horizontally disposed first bracket element accommodating the passage therethrough of one of said circular terminal portions of a heating element sheath, said bracket element having a substantially hexagonal collar gripping wall portions of said sheath to distort a very short length thereof into a shape conforming to said collar wall portions to prevent rotational or axial displacement of said sheath relative thereto,

and a vertical second bracket element integral with the first bracket element and fixed to a vertical side wall portion of said one of said bracket members, thefirst-named bracket element of each of said brackets being an identical distance below the plane occupied by the fiat coil portions of said heating elements.

3. A heating unit for surface cooking operations on an electric cooking range, comprising, in combination;

at least one heating element of the sheathed resistance conductor type arranged in a flat spiral coil, the sheath of said element throughout the coil portion thereof being substantially semi-circular in cross section with the flattened portion thereof occupying a horizontal plane to provide a platform for the support of a cooking vessel,

terminal end portions of said sheath extending vertically downwardly from said plane and being of circular cross section, said terminal end portions having a conductor adapted to carry the electrical energy to be supplied to said resistance conductor without substantial heating;

support means including structure having a plurality of radially extending arm members extending beyond the radially outermost convolution of said spiral coil and presenting coil-supporting surfaces in a horizontal plane;

and means for supporting said heating element with the sheath of the [flat spiral coil portion thereof free of said arm members and slightly above the plane of said arm members to permit substantially unrestrained lateral and vertical movements of said heating element convolutions, said supporting means including a horizontally disposed first bracket element accommodating the passage therethrough of one of said circular terminal portions, said bracket element having a substantially hexagonal collar, Wall portions of first said bracket element at a fixed distance below Which grip said sheath to distort a portion thereof the plane occupied by the spiral coil portion of said into a polygonal shape intermediate adjacent upper heating element.

and lower circular portions whereby to prevent rov tational or axial displacement of said sheath relative 5 References Cited in the fi Of this Patent therato, UNITED STATES PATENTS and a vertical second bracket element fixed to a side Wall of one of said bracket members to establish the 3016445 Llen 1962 

1. A HEATING UNIT FOR SURFACE COOKING OPERATIONS ON AN ELECTRIC COOKING RANGE, COMPRISING, IN COMBINATION: AT LEAST ONE HEATING ELEMENT OF THE SHEATHED RESISTANCE CONDUCTOR TYPE ARRANGED IN A FLAT SPIRAL COIL, THE SHEATH OF SAID ELEMENT THROUGHOUT SAID COIL PORTION THEREOF HAVING A FLATTENED UPPER PORTION DEFINING A HORIZONTAL PLANE TO PROVIDE A PLATFORM FOR THE SUPPORT OF A COOKING VESSEL, TERMINAL END PORTIONS OF SAID SHEATH EXTENDING VERTICALLY DOWNWARDLY FROM SAID PLANE AND BEING OF CIRCULAR CROSS SECTION; SUPPORT MEANS INCLUDING STRUCTURE HAVING A PLURALITY OF RADIALLY EXTENDING ARM MEMBERS EXTENDING BEYOND THE RADIALLY OUTERMOST CONVOLUTION OF SAID SPIRAL COIL AND PRESENTING COIL-SUPPORTING SURFACES IN A HORIZONTAL PLANE; AND MEANS FOR SECURING SAID HEATING ELEMENT TO SAID SUPPORT MEANS WITH THE SHEATH OF THE SPIRAL COIL PORTION THEREOF FREE OF SAID ARM MEMBERS TO PERMIT SUBSTANTIALLY UNRESTRAINED LATERAL AND VERTICAL MOVEMENTS OF THE FLAT SPIRAL COIL PORTIONS OF SAID HEATING ELEMENT, SAID SECURING MEANS INCLUDING A HORIZONTALLY DISPOSED FIRST BRACKET ELEMENT ACCOMMODATING THE PASSAGE THERETHROUGH OF ONE OF SAID CIRCULAR TERMINAL PORTIONS, SAID BRACKET ELEMENT HAVING A SUBSTANTIALLY HEXAGONAL COLLAR, WALL PORTIONS OF WHICH GRIP SAID SHEATH TO DISTORT A PORTION THEREOF INTERMEDIATE UPPER AND LOWER CIRCULAR PORTIONS INTO A POLYGONAL SHAPE CONFORMING TO SAID COLLAR WALL PORTIONS TO PREVENT ROTATIONAL OR AXIAL DISPLACEMENT OF SAID SHEATH RELATIVE THERETO, AND A VERTICAL SECOND BRACKET ELEMENT FIXED TO A SIDE WALL OF ONE OF SAID BRACKET MEMBERS TO ESTABLISH THE FIRST AND BRACKET ELEMENT AT A FIXED DISTANCE BELOW THE PLANE OCCUPIED BY THE FLAT SPIRAL COIL PORTION OF SAID HEATING ELEMENT, SAID COLLAR BEING SPACED FROM SAID SECOND BRACKET ELEMENT BY LESS THAN THE DIAMETER OF SAID SHEATH. 